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I may be incorrect, but it appears from the various scope shots and photos that he is not measuring directly across the CSR (I cannot see a scope gnd lead attached to the CSR), but is instead measuring voltage at two points, with one point including the CSR Vdrop. It appears that he then calculates the difference between the two waveforms to arrive at what he believes is the voltage across the CSR.

At the 33Kc or so frequency of the positive going voltage peak (calculated from time interval at FWHM), around 500nHy of inductance in the current sense loop would produce a 100% error in the current measurement (i.e., it would add add .1 ohms in series with the .1 ohm CSR), despite the CSR being non-inductive. 500nHy is equal to about 15 inches of straight wire.

If I am in error regarding my assumptions related to his use of the CSR and how he measured the voltage across the CSR, please feel free to enlighten me. Possibly someone can take a closer look at his photo and see if he does indeed have his probe and probe ground directly across the CSR. From what I can see zoomed in, it does not appear so.

It remains likely that his previous test using the light meter that indicated a 92% efficiency was closer to reality.

I may be incorrect, but it appears from the various scope shots and photos that he is not measuring directly across the CSR (I cannot see a scope gnd lead attached to the CSR), but is instead measuring voltage at two points, with one point including the CSR Vdrop. It appears that he then calculates the difference between the two waveforms to arrive at what he believes is the voltage across the CSR.

At the 33Kc or so frequency of the positive going voltage peak (calculated from time interval at FWHM), around 500nHy of inductance in the current sense loop would produce a 100% error in the current measurement (i.e., it would add add .1 ohms in series with the .1 ohm CSR), despite the CSR being non-inductive. 500nHy is equal to about 15 inches of straight wire.

If I am in error regarding my assumptions related to his use of the CSR and how he measured the voltage across the CSR, please feel free to enlighten me. Possibly someone can take a closer look at his photo and see if he does indeed have his probe and probe ground directly across the CSR. From what I can see zoomed in, it does not appear so.

It remains likely that his previous test using the light meter that indicated a 92% efficiency was closer to reality.

PW

I think I see both scope references attached to the coil end of the CVR.

However.... I am not convinced that the coil is hooked up as a Tesla bifilar ! It's not clear to me just how the coil is hooked to the lead-out wires. But I'll take his word for it for now.

Stefan's objection--- that the readings are taken at the peak of the outer envelope--- seems very damning. These cookers use the envelope modulation to control depth of penetration into the cooking pan (see the pdf). It's pretty clear from looking at the envelope-modulated waveform Stefan linked and those in the pdf file that the true overall average output power is going to be about half of that measured at the very peak of the envelope.

I'd like to see simultaneous waveforms from both the transmitting coil in the cooker, and the receiving coil. I will guess that the _transmitting_ coil in the cooker will show the same high "efficiency" when measured by the same method used for the receiving coil.

ETA: Yep, it's perfectly clear from the video that the envelope modulation is happening, and that Jean-Louis has computed his power output from the peak oscillations.

I think I see both scope references attached to the coil end of the CVR.

However.... I am not convinced that the coil is hooked up as a Tesla bifilar ! It's not clear to me just how the coil is hooked to the lead-out wires. But I'll take his word for it for now.

Stefan's objection--- that the readings are taken at the peak of the outer envelope--- seems very damning. These cookers use the envelope modulation to control depth of penetration into the cooking pan (see the pdf). It's pretty clear from looking at the envelope-modulated waveform Stefan linked and those in the pdf file that the true overall average output power is going to be about half of that measured at the very peak of the envelope.

I'd like to see simultaneous waveforms from both the transmitting coil in the cooker, and the receiving coil. I will guess that the _transmitting_ coil in the cooker will show the same high "efficiency" when measured by the same method used for the receiving coil.

ETA: Yep, it's perfectly clear from the video that the envelope modulation is happening, and that Jean-Louis has computed his power output from the peak oscillations.

Happy New Year TK (and all...),

I was looking at a photo that did not show that CSR board, it was hidden behind the unit. I see in the video (not sure it was there yet when I originally looked) and in the capture you posted, that he does indeed appear to be directly across the CSR, so pretty much everything I said in my previous post is moot! Assuming the bi-fi and lamp loads are floating "ground wise", all looks proper.

It probably would be a good idea for him to increase the distance between the induction coil and the CSR/probes/ground clip leads. Possibly some degree of induction is happening there and this could be easily tested by moving/re-orienting the CSR board during a measurement to see if scope display changes.

It is strange that the DSO measurement method yields almost exactly double the power out that the light meter method demonstrated.

Results are in very good agreement with the lightmeter result. Now the issue is tracking down the reason for the unusually high figure from the scope measurements.

Again, I suggest measuring the induction cooker's output coil directly and computing its power using the same scope settings as before. Then, "zoom out" the timebase and trigger the scope on the modulation envelope, showing two or three full cycles of the envelope, and let the scope recompute the power curve over a more realistic time interval, one which doesn't just count the peak values within one "fat" part of the envelope, but rather counts several cycles of the modulation envelope. My prediction is that using the same settings as before, the output coil will also show "overunity" but a little more than the receiving bifilar coil. I'll say it will be very close to 2000 Watts. Then when the zoomed-out envelope is measured, the average power will drop to around 1000 Watts, of which 96 percent is getting to the receiving bifilar coil.

I have quickly processed the data from Naudin's new test #5 measurements.

And I must say I'm a bit confused myself now :p. I calculated the power output using two different methods, one is using the mean the is using the root mean square. Both of these results should have given the same result or atleast very close to eachother, however in these calculations the average is lower than the RMS. Does anyone have a clue what might have caused this?